[omnibox] Add base::Feature kClobberIsZeroSuggestEntrypoint.

This CL just adds a base::Feature to guard the "clobber" as ZeroSuggest
entrypoint.

Adds it to about:flags too.

Bug: 1106096
Change-Id: I63f3dbdb60a986dd0fde58d8da3007603d8f2349
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2327844Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#793214}

chrome/browser/about_flags.cc

@@ -3612,6 +3612,11 @@ const FeatureEntry kFeatureEntries[] = {
      FEATURE_VALUE_TYPE(omnibox::kOmniboxTabSwitchSuggestions)},
 #endif  // defined(OS_ANDROID)
 
+    {"omnibox-clobber-is-zero-suggest-entrypoint",
+     flag_descriptions::kOmniboxClobberIsZeroSuggestEntrypointName,
+     flag_descriptions::kOmniboxClobberIsZeroSuggestEntrypointDescription,
+     kOsAll, FEATURE_VALUE_TYPE(omnibox::kClobberIsZeroSuggestEntrypoint)},
+
     {"omnibox-on-device-head-suggestions-incognito",
      flag_descriptions::kOmniboxOnDeviceHeadSuggestionsIncognitoName,
      flag_descriptions::kOmniboxOnDeviceHeadSuggestionsIncognitoDescription,

chrome/browser/flag-metadata.json

@@ -3186,6 +3186,11 @@
     "owners": [ "manukh", "chrome-omnibox-team@google.com" ],
     "expiry_milestone": 85
   },
+  {
+    "name": "omnibox-clobber-is-zero-suggest-entrypoint",
+    "owners": [ "tommycli", "chrome-omnibox-team@google.com" ],
+    "expiry_milestone": 95
+  },
   {
     "name": "omnibox-compact-suggestions",
     "owners": [ "ender", "chrome-omnibox-team@google.com" ],

chrome/browser/flag_descriptions.cc

@@ -1442,6 +1442,15 @@ const char kOmniboxAutocompleteTitlesDescription[] =
     "Allows autocompleting bookmark, history, and document suggestions when the"
     " user input is a prefix of their titles, as opposed to their URLs.";
 
+const char kOmniboxClobberIsZeroSuggestEntrypointName[] =
+    "Omnibox Clobber is ZeroSuggest Entrypoint";
+const char kOmniboxClobberIsZeroSuggestEntrypointDescription[] =
+    "If enabled, when the user clears the whole omnibox text (i.e. via "
+    "Backspace), Chrome will request ZeroSuggest suggestions. Note, this flag "
+    "merely adds a new ZeroSuggest entrypoint. ZeroSuggest still must be "
+    "enabled on the proper page classification (either by default or via a "
+    "separate flag), or else this flag will do nothing.";
+
 const char kOmniboxCompactSuggestionsName[] = "Omnibox: Compact suggestions";
 const char kOmniboxCompactSuggestionsDescription[] =
     "Conserve the space for Omnibox Suggestions by slightly reducing their "

chrome/browser/flag_descriptions.h

@@ -846,6 +846,9 @@ extern const char kOmniboxAssistantVoiceSearchDescription[];
 extern const char kOmniboxAutocompleteTitlesName[];
 extern const char kOmniboxAutocompleteTitlesDescription[];
 
+extern const char kOmniboxClobberIsZeroSuggestEntrypointName[];
+extern const char kOmniboxClobberIsZeroSuggestEntrypointDescription[];
+
 extern const char kOmniboxCompactSuggestionsName[];
 extern const char kOmniboxCompactSuggestionsDescription[];
 

components/omnibox/common/omnibox_features.cc

@@ -216,6 +216,14 @@ const base::Feature kOmniboxMaxURLMatches{
 const base::Feature kDynamicMaxAutocomplete{"OmniboxDynamicMaxAutocomplete",
                                             base::FEATURE_DISABLED_BY_DEFAULT};
 
+// If enabled, when the user clears the whole omnibox text (i.e. via Backspace),
+// Chrome will request ZeroSuggest suggestions. Note, this flag merely adds a
+// new ZeroSuggest entrypoint. ZeroSuggest still must be enabled on the proper
+// page classification (either by default or via a separate flag), or else this
+// flag will do nothing.
+const base::Feature kClobberIsZeroSuggestEntrypoint{
+    "OmniboxClobberIsZeroSuggestEntrypoint", base::FEATURE_DISABLED_BY_DEFAULT};
+
 // If enabled, ranks the local zero-prefix suggestions based on frecency
 // (combined frequency and recency).
 const base::Feature kOmniboxLocalZeroSuggestFrecencyRanking{

components/omnibox/common/omnibox_features.h

@@ -54,6 +54,7 @@ extern const base::Feature kOmniboxMaxURLMatches;
 extern const base::Feature kDynamicMaxAutocomplete;
 
 // On-Focus Suggestions a.k.a. ZeroSuggest.
+extern const base::Feature kClobberIsZeroSuggestEntrypoint;
 extern const base::Feature kOmniboxLocalZeroSuggestAgeThreshold;
 extern const base::Feature kOmniboxLocalZeroSuggestFrecencyRanking;
 extern const base::Feature kOnFocusSuggestions;

tools/metrics/histograms/enums.xml

@@ -41251,6 +41251,8 @@ from previous Chrome versions.
   <int value="-593536514" label="ExperimentalTabController:enabled"/>
   <int value="-591874964" label="LiteVideo:enabled"/>
   <int value="-589096918" label="ash-enable-fullscreen-app-list"/>
+  <int value="-588669613"
+      label="OmniboxClobberIsZeroSuggestEntrypoint:enabled"/>
   <int value="-582870536" label="BluetoothNextHandsfreeProfile:enabled"/>
   <int value="-579192400" label="disable-input-view"/>
   <int value="-577982497" label="CupsPrintersUiOverhaul:enabled"/>
@@ -42213,6 +42215,8 @@ from previous Chrome versions.
   <int value="480677983" label="WebXRARDOMOverlay:disabled"/>
   <int value="481506759" label="ServiceWorkerScriptStreaming:enabled"/>
   <int value="482232604" label="PercentBasedScrolling:enabled"/>
+  <int value="482429100"
+      label="OmniboxClobberIsZeroSuggestEntrypoint:disabled"/>
   <int value="485957747" label="finch-seed-ignore-pending-download"/>
   <int value="487810392" label="EnablePalmOnToolTypePalm:enabled"/>
   <int value="491334698" label="ConditionalTabStripAndroid:enabled"/>